Lifting jack



J. C.KOPF.

LIFTING JACK. APPLICATION FILED AUG.23, 1920.

3 SHEETS-SHEET I- g4; Egg) lln By Patented Mar. 28, 1922.

J. C. KOPF. unmc JACK. APPLICATION 'FILED AUG-23, 1920.

1,410,578. Patented Mar. 28, 1922'.

3 SHEETSSHEET Z- 7%NTOR.

J. C. KOPF. LIYFIING JACK. APPLICATION FILED AUG-23. 1920.

3 SHEETS-SHEET 3- ATEY Patented Mar. 28, 1922.

fijar JOHN C. KQPF, OF BELLEVUE BOROUGH, PENNSYLVANIA, ASSIGNOR TO THE DUFF MANUFAGTURING COMPANY OF, PITTSBURGH, PENNSYLVANIA, A COR/HORA- LIFTING JACK.

To all 207mm it may concern:

Be it known that I, Jot-IN G. Kerr, a citi- Zen of the United States, and a resident of the borough of Bellevue. in the county of Allegheny and State of Pennsylvania, have invented new and useful Improvements in Lifting Jacks, of which the following is a specification. r

The invention relates to. jacks, and more particularly to worm-operated lifting jacks; and the object is to provide a simple, reliabl and easily operated device.

The class of jacks with which the in vention is concerned employs lifting worms the pitch of which is beyond the angle of repose, instead of being self-locking like ordinary worms, the advantage being reduction in end-thrust resistance to manual operation in lifting and lowering, created by the load acting through the jacking mem-' her and gearing upon the worm, and also the higher speed ratio between the worm and worm-wheel. In order to sustain the load it has been customary to provide a constantly applied adjustable brake-band or frictional resistance. This must be set ti 'ht enough to hold the heaviest load, so that its resistance is greater than is required for lighter loads. Furthermore, the brake must be taken up from time to time to compensate for wear, the extent and times of such adjustment being uncertain, with the result that the use of the jack may be made unnecessarily laborious, or that it may fail and allow the load to drop.

By the present invention, the frictional resistance which must be overcome in operating the lifting worm by the ratchetflever on its shaft is automatically proportioned to the load, and no adjustment is required. Consequently a jack is provided in which the labor is as light as possible, and which is inherently safe.

In the accompanying drawings, forming part hereof:

Figure 1 is a front elevation of the jack, with the cover removed;

Fig. 2 is a side sectional elevation on the line 22 of 1;

Fig. 3 is a horizontal section in the plane of the axis of the operating shaft, which is seen in plan; and

Figs. l to 7 are detail face and edge views of the friction disks.

Specification of Letters Patent.

Application filed August 23,1920. Serial No. 405,401.

The 'ack has a stand frame 1, in which a jaclt' 1 ar or jacking member 2, provided with rack teeth 3 on one side, is verticallv guided. v

The rack teeth are meshed by a pinion cut on a shaft 5, which is journaled in front and rear bearings 6 and in a gear case 8, the bearing 6. being removable to permit the insertion of the pinion into its rear chamber 9. On the forward part of the pinion shaft, in a front or outer chamber 10 of the gear case, rendered accessible by a cover 11, is a worm-wheel 12, larger than the pinion.

A single main operating shaft is arranged transversely below the aXis of the pinion and worm, in bearings half in the body of the frame and half in the cover 11; and on this shaft, within the chamber 10, is a worm 1t meshing the worm-wheel. A. lever rocker or ratchet case 15. socketed for the reception ofa' handle bar and containing a double reverslble pawl 29, is mounted to oscillate on the outwardly projecting portion of this shaft, in cooperation with a ratchet wheel 16 fixed on a hexagonal seat 1?. The spring 30 pressing the pawl serves to hold the latter in position for either lifting or lowering.

W'hen load is on the rack-bar, whether at rest, or when lifting or lowering by means of the ratchet'lever, the action of the load is transmitted and reduced through the ge-.-ing and applied to the worm, where becauseof the pitch its effect is partly to rotate the worm '14 and partly to press it endwise, creating a constant moderate end- .thrust pressure, toward the right in Fig. 1.

Between this end of the worm and the frame there are introduced, according to this invention, two disks 18 and19, having flat smooth surfaces to cooperate with each other and with similar surfaces 20 and 21 formed on the end of the worm and the interior of the frame. The disk 18 has a round central opening 22 encircling the shaft, and an external notch 23 which engages an anchoring rib 24 projecting from the rear wall of the chamber 10 of the frame. This disk is thus held against rotation, while free to be pressed axially against the disk 19. The latter disk is engaged to rotate with the shaft. while alsofree axially, by means of lateral notches 25 in its interior opening 26 and a cross-pin 27 in the shaft, the ends of which project into the notches. There are thus three friction surfaces which are rotatable with the shaft and worm, and three opposed surfaces which are stationary in respect to rotation, the alternating fixed and rotatable elements being adapted to be compacted by the end-thrust against the abutment support of the frame. Through the friction thus produced, the load is securely held by its own action against running down, the holding being proportional to the load; so that the lighter the load the less the resistance. Thus, the friction, while always sufficient to hold the load, is easily overcome by the handle lev ,1- age upon the operating shaft in lifting and lowering. .ln lowering, the load seeks to turn the worm and consequently it is necessary only to overcome the excess friction between the surfaces.

Additional pressure of small amount is provided by a light spring 28 encircling the shaft between the other end of the worm and the remote wall of the chamber. This spring serves to prevent the ratchet Wheel 16 being dragged back by the spring-pressed pawl 29 on the upstrokes 0f the lever, when the .jack bar is being raised to the load. With no load on the jack, the tendency would be merely to oscillate the worm idly back and forth; and the spring produces sufficient initial friction between the holding surfaces-t0 obviate this.

While the preferred form of the invention has been described in detail it will be understood that numerous changes may be made without departing from essentials.

. What I claim as new is:

1. A jack, comprising a rack-bar, a pinion meshing. therewith, a worm-wheel connected with the pinion, a quick-pitch lifting worm meshing the worm-wheel and continuously exerting end-thrust in one direction when load is on the jack, frictionholding means actuated by said end-thrust, and means for turning the worm against the friction of said means to operate the rack-bar.

In a jack, the combination of a frame. a jacking member, a single operating shaft, a quick-pitch lifting worm on said shaft, with gearing through which the worm actuates the jacking member and through which the load acts upon the worm, and friction holding means between one end of said lifting worm and the frame, to be actuated by the end-thrust of the worm under load.

3. In a jack, the combination with a f "Mac, a jacking member, an operating shaft, and gearing for actuating the jacking member, including a quick-pitch worm on the operating shaft, of friction holding means between one end of the worm and the frame, to be actuated by the end-thrust of the worm under load, and a spring applying pressure at the other end of the worm.

at. In a jack, the combination with a jacking member andmeans for operating the same comprising an operating shaft, a quick-pitch worm thereon, with gearing through which the worm actuates the jacking member and through which the load acts upon the worm, and ratchet lever means for operating the shaft, of friction holding means actuated by the end-thrust of the worm under load, and a spring for applying initial pressure to the holding means.

A jack, comprising a frame, a rack-bar, a pinion meshing said bar, a worm-wheel connected with the pinion, an operating shaft, a lifting worm on said shaft meshing the worm-wheel, and friction holding elements alternately connected with the shaft and held against rotation by the'frame and arranged to becompacted by the endthrust of the lifting worm under load.

6. rbjack, comprising a frame provided with an anchoring rib, a rack-bar, a pinion meshing said bar, a worm-wheel connected with the pinion, a main operating shaft, a lifting worm on said shaft meshing the worm-wheel, a friction disk encircling the shaft at the end-thrust end of the worm and loosely engaged with said rib, and another friction diskloosely engaged with the shaft between the aforesaid disk and the face of the fixed frame.

7. In a jack, a frame provided with an 3 anchoring rib, a jacking member, a single operating shaft, gearing for actuating the jacking member, including a worm on the operating shaft, and stationary and rotatable flat friction disks subject to the endi thrust pressure of the worm under load, loosely engaged respectively with said rib and with the shaft.

JOHN C. KOPF. 

